关键词: 城市化, 氮补偿, 京津冀区域, 活性氮, 数据包络分析

Abstract: Coarse woody debris (CWD) includes standing dead trees and stumps, whole fallen trees and dead branches on forest floor. CWD is an important structural component of many forest ecosystems and plays a key role in a number of aspects of ecosystem function. CWD contributes substantially to the long-lived forest carbon pool， however, CWD is often overlooked in forest carbon inventories. CWD varies highly in different forest zones. CWD volume in the world and CWD carbon storage in the United States and China decreases with decreasing the latitude. Studies of naturally regenerated forests typically report a “Ushaped” temporal pattern of CWD. Other temporal patterns have also been noted. Occasionally, stands exhibit no clear temporal pattern at all. Local environmental conditions, in particular temperature and humidity, exert strong controls on the rate of CWD decomposition. Species-based variation in wood traits may also contribute to the observed variations in CWD decomposition. There are rich forest types in China, which provides favorable conditions for CWD study. A number of studies about storage and decomposition of CWD have been conducted in China. However, all of them are still far away from the advanced level. A combination of field surveys, long-term experiments and model simulation should be required to ascertain the current and future status of CWD carbon stocks.

Key words: urbanization, data envelopment analysis, Beijing-Tianjin-Hebei agglomeration, nitrogen offset, reactive nitrogen